1. Technical Field
The present invention relates to an on-running landing position evaluation method and the like. The invention further relates to a detection method for detecting user's landing and takeoff and the like. The invention further relates to a running motion evaluation method for evaluating the user's running motion and the like.
2. Related Art
A portable electronic apparatus attached to a body portion or an arm of a user who does a sport, such as running, is widely used. Some popular portable electronic apparatus of this type having been developed have a variety of built-in sensors, such as an acceleration sensor and a gyro sensor, and have a function of calculating a variety of data of the sport, such as the position, the running speed, the heart rate, the number of footsteps, and the running pace by using detection values from the built-in sensors (see JP-A-2013-140158, for example).
Further, there is a known portable apparatus of related art that is attached to a user who is running and periodically measures and displays information on the user's position and speed, information on travel distance, and other types of information.
Still further, there is a technology for displaying motion images of a virtual runner on a display section of display glasses that the user wears around the head in order to allow the virtual runner to contribute to achievement of a good record (see JP-A-2014-054303, for example).
To work on running in an attempt to achieve a good record, only being aware of the running speed is insufficient, and it is important to be aware of the state of body motion, such as a running form. The reason for this is that when a person runs in a good form, not only can it be expected that the person achieves a good record, but also the person can run for a long period with fatigue accumulation and risks of injury and other types of failure lowered. A known example of a technology for analyzing a running form by using an apparatus attached to a user who is running is the technology described in JP-A-2013-106773.
Further, one of indices for evaluation of the motion state is, for example, an on-ground duration. It is believed that a long in-air duration achieves a long stride and results in a short on-ground duration for improvement in running speed. In addition, a short on-ground duration can reduce a burden acting on the legs during running motion. It is therefore meaningful for a runner to know an index relating to the on-ground duration (hereinafter referred to as “evaluation index value”) because the knowledge leads to being aware of the state of the runner's motion.
However, in addition to recording daily running exercise, it is convenient and desired to have a kind of coaching function of evaluating running itself, such as the running form, and notifying a user of an evaluation result. For example, a landing position in running motion is one running evaluation index, and it is believed desirable that a runner lands on the ground in a position roughly immediately below the center of gravity of the runner (landing immediately below). The reason for this is that landing on the ground in a forward position from the center of gravity causes braking force to act on the runner, whereas landing on the ground in a position roughly immediately below the center of gravity reduces the braking force resulting from reaction from the ground. The landing immediately below provides another advantage of a decrease in the amount of upward-downward movement of the center of gravity. All things described above considered, the landing immediately below is believed to achieve energy-efficient running.
Methods of related art for evaluating the landing position in running motion, for example, use motion capture, video image capture, and a floor reaction force meter. Each of the methods of related art, however, needs to install a large-scale system and requires a user to run a route where the system is installed. The location where the user can actually run is therefore limited, and it is substantially impossible to continuously evaluate running over a long distance for a long period. A typical runner is undesirably not allowed to make casual use of any of these methods.
Further, to calculate the on-ground duration, it is necessary to detect the timing when a leg lands on the ground and the timing when the leg takes off the ground. No specific technology for precisely detecting the landing timing and the takeoff timing with a sensor attached to a user has been known.
Another index for evaluation of the motion state is propulsion efficiency. The propulsion efficiency represents how long a runner has traveled forward in response to applied force, more specifically, how efficiently the runner converts reaction force from the ground in an on-ground duration into propulsion that moves the runner' body in the advance direction. It can therefore be said that reduction in body movement in directions other than the advance direction allows efficient propulsion generation, and that reduction in upward/downward movement due to jump at the time of takeoff and subduction at the time of landing and reduction in rightward/leftward runout allow improvement in the propulsion efficiency. In particular, the movement in the upward/downward direction, which coincides with the direction of gravity, greatly affects the propulsion efficiency.
JP-A-2013-106773, for example, focuses on the point described above and describes analysis of a running form from a viewpoint of smallness of the upward/downward movement and diagnosis of body action. It is, however, actually difficult in some cases to evaluate the quality of the propulsion efficiency only from the upward/downward movement.